There are a variety of methods practiced for measuring changes in fluorescence yield under varying light intensities. Different kinds of fluorometer devices have been developed to implement such methods. One such known method is to use the so-called "pump and probe" technique in which the change in fluorescence yield of a relatively low intensity probe flash is measured following a pump flash which is usually made intense enough to saturate the observable effect. An example of one type of known fluorometer device that uses a steady source of light from a lamp in combination with a flash of light to bring about transient fluorescence is described in U.S. Pat. No. 4,650,336, which issued Mar. 17, 1987. While that device makes it possible to take certain desirable measurements of plants, as do other known prior art fluorometers, there remains a need for more accurate and readily usable fluorometer devices to provide such desired measurements.
A primary object of the present invention is to provide a programmable, computer controlled fluorometer device that is operable to readily provide a number of different measurements of photosynthetic activity, by means of precisely following changes in fluorescence yield of relatively weak probe light, preceding and succeeding a stronger actinic pump flash of light.
Another object of the invention is to provide a conveniently portable and submersible version of such a fluorometer device to enable the taking of such measurements from submerged plants and phytoplankton.
Yet another object of the invention is to permit such an operable fluorometer device to use programmable commands, readily variable pump and probe flash intensities and increments, and readily variable delays in sequences of pump and probe flashes, in order to afford measurement of maximum fluorescence yields, optical absorption cross sections, and turnover times of photosynthetic samples under either darkness or ambient irradiance conditions.
Still another object of the invention is to provide a fluorometer device that can independently measure cross sections and turnover times of photosynthetic organisms under their normal ambient conditions, such as in undersea environments.
A further object of the invention is to enable measurement of such photosynthetic parameters of plants and phytoplankton as level of variable fluorescence, absorption cross-section of Photosystem II, turnover time of photosynthesis, and estimation of the energy transfer among the Photosystem II units. Additionally, the invention will enable measurement of the on-going photosynthetic production rates under ambient light conditions.
Yet another object of the invention is to provide a submersible instrument that enables the same measurements to be done in situ, in the ocean. Additionally, application of the device should allow estimation of the relative growth rates of phytoplankton.
Additional objects and advantages of the invention will become apparent from the description of the invention that is presented below.